From German Open Application DE-OS 25 25 232, it is known to provide a device for the control of a filter centrifuge in response to signals generated by a swingable arm which contacts the free surface of the centrifuge contents during rotation of the filter centrifuge drum. Level-measuring or filling-measuring signals may be outputted by the feeler arm.
Utilizing this technique, it is possible to ascertain the thickness of a layer on the centrifuge drum, i.e. the degree of filling of the centrifuge drum by the contents thereof.
For example, the information thus provided may be used to control the addition of the suspension to the filter drum, to terminate the filtering operation or for some other purpose.
A disadvantage of this device is that it can only provide information relating to the thickness of the layer of material on the filter drum and cannot indicate anything as to the characteristics of the centrifuge contents. It cannot, for example, indicate whether the free surface of the contents of the drum is that of the suspension which is to be filtered, washing liquid, or solids of the filter cake which is formed as the liquid phase is centrifugally expressed through the solids.